Calorimeter



Sept. 21, 1954 c. H. BARNARD ETAL CALORIMETER Filed March 21, 1950INVENTURS AND CLAYTON H. BARNARD JAMES E. MQEVOY BY A RNEY mwEo E4Patented Sept. 21, 1954 2,689,478 CALORIMETER Clayton H. Barnard, SouthEuclid, and James E.

McEvoy, East Cleveland, Ohio. assignors to Bailey Met-er Company, acorporation of Dela- Ware Application March 21, 1950, Serial No. 150,962

4 Claims. 1

Our invention is in connection with calorimany, and specifically offersan apparatus for compensating gas calorimeters which determine the lowerheating value of gaseous combustibles so that the higher heating valueof the combustibles may be obtained.

In the United States commercial, gaseous fuel is usually sold tocustomers on the basis of its higher heating value. Objection is raisedwhen comparison is made to countries or cities which base their rate onthe lower heating value. It might be possible to meet the objection ifthe high and low heat values maintained a constant ratio as theconstituents of the fuels varied. It would then appear that a customerin the United States obtained a consistently proportional amount of heatfor his money compared with the continental user, and the problem ofobtaining equality would evolve into a simple matter of economics.

However, the ratio of higher to lower heat values varies with thehydrogen content of the fuels. Therefore, the United States customerfinds that the high heat value of his fuel mounts with hydrogen contentincrease while his cost rises as some definite function of suchincrease. However, the heat actually available, namely the lower heatvalue, does not rise by the same function.

By theterm heat available reference is to that quantity of heat of thecombustion proc ess which the customer ordinarily transfers to a workingfluid by a heat exchanger. Commercial heat exchangers do not utilize theheat residual within the steam of combustion as heat oivapor ization,exhaustion of the products of combustion taking place prior tocondensation.

As traditional usage continues to influence the system of chargingconsumers on thekbasis of higher heating value there remains the need ofa device to continuously determine both values to enable manufacturersto control the quality of their product and calculate charges to theircustomers.

The present invention, therefore, is novel in its provision of means fordetermining the difierence between the higher and lower heating value ofgaseous fuels and which may be used to compensate the lower heatingvalue from calorimeters.

Another object of the present invention is to provide an instrumentwhich is accurate and in which the accuracy of its various componentscan be easily checked.

An additional obj ect' of the invention is to pro:

2 vid'e an instrument whose indication is dependent only upon the heatvalues of the fuel.

Another object of our invention is to provide an instrument which willbe fully automatic and which will present either a visual indicationand/ or a record on a moving paper or other article.

The figure presented represents a schematic view through the principalparts of a calorimeter assembly by which our invention compensates forthe high-heat value. of the gas analyzed;

The calorimeter is of the continuous-flow, gaseous, re-heat typecomprising a body I having combustion, reheat and heat exchangesections.

.7 Carrier air is supplied through controller 2 which maintains aconstant pressure-by having a relay 3 similar to that disclosed in thepatent to Gorrie Re. 21,804 magnify pressure variations upon thediaphragm of a standard pressure-reducing valve 4 to maintain thepressure of the air constant.

A constant-volume pump 5, actuated by an electric motor, simultaneouslysupplies test samples of the gas to be analyzed to the burner 6 inthecombustion section of I and to the burner 1 in a second combustionchamber of our invention. With the gas supply system maintained at aconstant temperature sufficiently high above ambient fluctuationsby thepump 5 enclosure,

thermostatically controlled with a simple electric heater, the densityof the gas varies as a function ofbarometric pressure which isregistered upon the bellows of transducer 8 for compensating thefundamental measuring circuit which forms the subject matter or a,copending application A ,J. Hornfeck Serial No. 150,850, filed March21,

to dissipate energy within the box enclosure of pump 5. A thermostat 5Bis shown example of a simple temperature sensitive device which can bearranged within the pump 5 en closure for control of a heatingdevice,sueh 5A, through relay 50.

As explained in the Hornfeck application. transducer 8 unbalances acircuit which motor controller ampline'r 9 tends to maintain in balance.While restoring balance through motor (0, amplifier 9 positions voltagedivider II which divides the reference voltage of the fundamentalcircuit of the calorimeter.

The carrier air from pressure controller 2 is heated by the combustionof the sample gas at bu'rr'ier 6 and the temperatures before and afterthe burner are detected by ther'rno units 12 and I3. The carrier air isthen passed in heat eX- The electric heater is shown at 5A :as arrangedchanging relationship with carrier air continuously entering body I fromcontroller 2 to cool it to a temperature which both streams going to thecombustion and reheat sections equal. Then the cooled carrier air isre-heated by heater l l and its temperatures before and after there-heating are detected by thermo elements l5 and I6.

Of course products of combustion are added in the combustion sectionwhich alter the specific heat of the stream going to the reheat section,but with the ratio of carrier air to gas standing at about 500 to 1, thedifierence is deemed to alter negligibly the amount of re-heat neededfor thermal balance.

The thermo units I2l3l5l6 are made to form the legs of a Wheatstonebridge whose unbalance is detected by motor controller-amplifier I!which then adjusts the electrical power to re-heater M. by having motorl8 position a rheostat [9 in the circuit of heater I4.

The fundamental'measurement is performed by maintaining balance in thecircuit of a reference voltage source 29 and the voltage across theheater Id. The unbalance of this circuit is detected bymotor'controller-amplifier 22 which simultaneously positions aresistance arm 23 and an indicator 24 through motor 25 and cam 24A. Withnothing other than the variation in constituents of the gas to unbalancethe fundamental circuit, the final indication by 24 is of the lowheatvalue of the fuel. Only the lower or net heating value of the fuel isreleased in the combustion chamber and matched by the re-heater output.The circuit may be calibrated for range of heat values with resistance Aand given a suppression of the range with resistance I IA and 23A. Withthe test gas preheated to a level where its density is unafiected byambient variations, the cam 24A may be shaped to give the low-heat valueof the gas at whatever barometric pressure exists. The barometricpressure variations may be calculated into the circuit, as indicatedsupra, by positioning resistance arm I I so that it divides thereference voltage of 20, and the final indication of low-heat valueswill be as of gas at standard, or some predetermined, pressure as wellas standard temperature.

Our invention further alters the balance of the fundamental circuit byadding to the voltage across the heater M in proportion to the value ofthe difference between the higher and lower heating values of the gas.The voltage across the heater at 2! is added to by resistance 26inserting a portion of the potential of source 21 into the fundamentalcircuit. Resistance 26 is positioned by motor 28, controlled by motorcontroller-amplifier 29 sensitive to unbalance in the Wheatstone bridgegenerally designated at as.

Our invention, then, supplies the additive factor to the lower heatingvalue of the gas, and this is specifically determined in the followingmanner. 'The sample gas is burned at burner 1 g in combustion chamber 3|which is supplied a carrier air which is dried until its absolutehumidity is substantially zero.

The volumes of air and gas are adjusted to raise the humidity of the airresulting from the addition to it of combustion water to the range of ahumidity detecting device. The carrier air of the combustion chamber isgiven a back pressure by adjusting the chamber cover until a flowthrough chamber 32 results. A hole is provided in this chamber 32 sothat the carrier air, with its raised humidity, passes over humiditydetector 33.

In the present instance detector 33 is given the characteristics of awell-known type of hotbulb hygrometer called a Dewcel. Essentially theDewcel comprises two filaments supplied from a source 34 and in circuitcompletion through a quantity of lithium chloride which allows currentpassage in the circuit in proportion to the moisture the lithiumchloride absorbs. The resulting heat of the completed circuit tends todry the lithium chloride and prevent current flow so a balance isattained between the humidity of the carrier air passing over the Dewceland its resulting heat. Thus the Dewcel assumes a temperature which isrelated to the partial pressure of the water vapor in the air, or thelbs. of water per lb. of dry air. It is, therefore, a measure of theweight of water formed from the combustion of a constant volume of gas,provided the lbs. of dry air furnishedto the combustion chamber do notvary.

Since the difference between the higher and the lower heating value of agaseous fuel is directly dependent on the quantity of water formed fromthe combustion of the gas, it is evident that any means whereby the lbs.of water formed per cu. ft. of gas burned can be determined oiiers ameans of fixing the difference between the higher and lower heatingvalues.

A leg of Wheatstone bridge 30 is arranged so that it is sensitive to theDewcel heat and is therefore unbalanced in proportion to the lbs. ofwater formed per cu. ft. of gas burned.

Should the high-heat compensator have its source 34 disconnected for anysubstantial length of time, the lithium chloride will absorb moisture tothe point that re-application of the source 34 will cause such a highcurrent to flow in the Dewcel circuit that the resulting heat may damagethe structure. Consequently, a valve in the form of a conventionaltungsten lamp 35 has been found capable of effectively limiting thecurrent until the lithium chloride is dried out to its proper range ofresistance.

In the discussion, supra, of the method of arriving at the differencebetween the high-heat and low-heat values of the gas it was assumed thatthe lbs. of carrier air furnished per cu. ft. of gas burned would remainconstant. Ambient temperature and barometric pressure fluctuations makethis impossible. The weight of air flow will vary as the square root ofthe density, since its flow depends on a differential. However, it isobserved that the pressurefluctuations to be normally expected will besmall (about 2% max.) and those from temperature about 3% max.Deviations in the gas weight from that at standard vary directly withthe density and are found to not exceed .5% of the total heat value ofthe gas. Thus our invention is practical in operation with the meansdisclosed controlling all necessary variables.

What we claim as new and desire to secure by Letters Patent of theUnited States is:

1. A calorimeter for gaseous 'combustibles of the continuous flowre-heat type comprising, means for supplying gas at a constant volumerate, means for supplying carrier air at a constant weight rate andabsolute humidity of substantially zero, chamber means for burning thecombustible in the carrier air, means for detecting the humidity of thecarrier air without substantially reducing its humidity, means for passing the carrier air over the means for detecting the humidity, abalanceable network including the humidity detector which is unbalancedin accordance with a change in magnitude of the humidity detected, ameans sensitive to the unbalance of the network, a means under controlof the sensitive means for restoring the balance of the network andsimultaneously indicating the rebalanced motion as the difierencebetween the higher and lower heat values of the gas.

2. An apparatus for giving a response in accordance with the variationbetween the higher and lower heating values of a gaseous combustiblecomprising, means for supplying a carrier air at constant weight rateand substantially zero absolute humidity, means for supplying thegaseous combustible at a constant rate, chamber means for combustion ofthe gaseous combustible in the carrier air, means for detecting thehumidity in the carrier air after the combustion without substantialhumidity reduction of the carrier air as an indication of the differencebetween the higher and lower heating value of the gas, means for passingthe carrier air over the humidity detector, an electrical networkincluding and unbalanced by the humidity detector, means sensitive to anetwork unbalance, and means controlled by the sensitive means forgiving a mechanical movement in the direction and to the extent of thevariation of the difierence between the higher and lower heating valueof the gas.

3. Apparatus for giving a response in accordance with the variationbetween the higher and lower heating value of a gaseous combustible com-1 prising, means for supplying gas at a constant volume, means forsupplying combustion air at constant weight, means for reducing theabsolute humidity of the combustion air to approximately zero, a,combustion chamber for the gas and air for the formation of combustionwater vapor, a detection chamber for humidity, means for causing flow ofthe air and combustion water vapor through the detection chamber, ahumidity detector whose temperature rise is a known function of the lbs.of water per lb. of air, a Wheatstone bridge network unbalanced by theheat of the humidity detector on one leg, means sensitive to theWheatstone bridge unbalance, and means controlled by the sensitive meansfor giving a mechanical movement in the direction and to the extent ofthe variation of the difierence between the higher and lower heat valueof the gas as evidenced by the intensity of the heat of the humiditydetector.

4. A continuous flow calorimeter of the gaseous re-heat type including,combustion and re-heat sections joined by a heat exchanger as a body, ameans of supplying the sections sequentially with definite volumetricproportions of a gaseous combustible and carrier air, means formaintaining the gas supplied at a level of temperature wherein transientambient temperature changes will not change its density, an electricalnetwork sensitive to temperatures in the combustion and re-heat sectionsand unbalanced by a difference in temperature rises of the carrier airthrough the sections of the body, means for detecting the unbalance ofthe network, means for dissipating energy input to the re-heat section,means for regulating the input to the re-heat section under the controlof said detector, means for indicating and recording the input, acombustion chamber separate from the body, means for supplying thecombustion chamber with definite volumetric proportions of the gas anddry carrier air, means for measuring the moisture added to the drycarrier air by the burning of the gas in units common with the re-heatenergy, and means for increasing the manifestation of input to there--heat section by the difference between the higher and lower heatingvalues of the gas as represented by the manifestation of the combustionwater produced in the separate combustion chamber.

References Cited in the file of this patent UNITED STATES PATENTS NumberName Date 1,997,383 Junkers Apr. 9, 1935 2,026,179 Keith Dec. 31, 19352,026,180 Keith Dec. 31, 1935 2,359,278 Allen et al. Oct. 3, 1944FOREIGN PATENTS Number Country Date 902,952 France Jan. 3, 1945

